Background and objective: Patients with chronic obstructive pulmonary disease (COPD) and chronic hypercapnic respiratory failure (CHRF) characteristically have exercise intolerance and limitations in performing conventional training. Therefore, the aim of this study was to investigate the acute effects of non-invasive ventilation (NIV) as a supportive tool during exercise in CHRF.
Methods: Two cycle endurance tests (CET) at 60% of the peak work rate were performed. Patients were randomly assigned to cycle in two conditions: (i) high-pressure NIV (mean inspiratory positive airway pressure: 27 ± 3 cm H2 O) along with oxygen supplementation or (ii) control: oxygen-use only. Transcutaneously measured partial pressure of carbon dioxide (TcPCO2 ), oxygen saturation and heart rate were continuously recorded. Muscle oxygen availability of intercostal and vastus lateralis muscle was measured during exercise by near-infrared spectroscopy (NIRS).
Results: A total of 20 patients with CHRF (forced expiratory volume in 1 s (FEV1 ): 19 ± 4% predicted, partial pressure of oxygen (PaO2 ): 55 ± 9 mm Hg, partial pressure of carbon dioxide (PaCO2 ): 51 ± 7 mm Hg) were recruited in a randomized cross-over trial. On NIV, COPD patients increased cycle endurance time by 39% compared to oxygen-use only (663 ± 360 vs 477 ± 249 s, P = 0.013). On NIV, TcPCO2 was significantly lower at rest (44.9 ± 6.2 vs 50.7 ± 6.6 mm Hg, P < 0.001) and at isotime (50.0 ± 5.5 vs 56.1 ± 6.2 mm Hg, P < 0.001). Oxygen availability in the intercostal muscles remained relatively constant with NIV compared to oxygen-use only. Although patients cycled longer using NIV, a lower increase in exertional dyspnoea at the end of CET (median increase in Borg-dyspnoea: 2 vs 4, P = 0.003) was reported.
Conclusion: NIV with high pressures as add-on to oxygen supplementation increases cycle endurance time, mitigates exertional dyspnoea and limits exercise-induced hypercapnia in COPD patients with CHRF.
Trial registration: ClinicalTrials.gov NCT02877290.
Keywords: chronic obstructive pulmonary disease; exercise and pulmonary rehabilitation; hypercapnia; ventilation.